The male fern is one of the most popular and effective treatments for tape worms. The root stalks are anodyne, antibacterial, anti-inflammatory, antiviral, astringent, febrifuge, vermifuge and vulnerary[7, 9, 13, 19, 21, 171, 178, 218, 238]. The root contains an oleoresin that paralyses tapeworms and other internal parasites and has been used as a worm expellent[222, 238]. The active ingredient in this oleo-resin is 'filicin', roots of this species contain about 1.5 - 2.5% filicin[240]. It is one of the most effective treatments known for tapeworms - its use should be immediately followed by a non-oily purgative such as magnesium sulphate, Convolvulus scammonia or Helleborus niger in order to expel the worms from the body[7, 238, 254]. An oily purge, such as caster oil, increases the absorption of the fern root and can be dangerous[238]. The root is also taken internally in the treatment of internal haemorrhage, uterine bleeding, mumps and feverish illnesses[238]. The root is harvested in the autumn and can be dried for later use[7]. This remedy should be used with caution and only under the supervision of a qualified practitioner[21, 238]. The root is toxic and the dosage is critical[238]. Pregnant women and people with heart complaints should not be prescribed this plant[7]. See also notes above on toxicity. Externally, the root is used as a poultice in the treatment of abscesses, boils, carbuncles and sores[238, 268].